After months of closed-door negotiations with a handful of senators on the Finance Committee, which Mr. Baucus leads, the full panel now gets to put its imprint on what could be landmark legislation to overhaul the health system.

Senators have offered 564 amendments, all posted on the committee Web site, and the Republican proposals generally reveal seemingly irreconcilable differences. While they would gut the bill, one Republican, Senator Olympia J. Snowe of Maine, wants important changes but appears ready to get behind it, provided Mr. Baucus can keep his fellow Democrats in line.

For Mr. Baucus, the challenge will be to stop his fellow Democrats  they outnumber Republicans 13 to 10  from shifting the bill so hard to the left that they chase away Ms. Snowe, who could provide the crucial 60th vote needed to get the measure through the Senate.

Consider Ms. Snowe’s most important amendment: to trigger the creation of a government-sponsored insurance plan in any state that fails to provide affordable insurance to 95 percent of residents. Mr. Baucus will have to fend off powerful Democrats, including Senators John D. Rockefeller IV of West Virginia and Charles E. Schumer of New York, who want to create the public plan from the outset.

The proceedings promise to be a wild ride for other reasons. Senator John Ensign, Republican of Nevada, wants to delete the word “fee” everywhere it appears in the bill and replace it with the word “tax,” a signal that Republicans intend to oppose the bill by framing it as a huge tax increase.

Senator Charles E. Grassley, Republican of Iowa, who along with Ms. Snowe engaged in months of intense negotiations with Mr. Baucus, would do away with a core component of the proposal  a requirement that virtually all Americans obtain health insurance or pay a penalty if they fail to do so.

And Mr. Grassley would eliminate proposed fees on the health industry, including insurers, drug companies and device manufacturers. Instead, he would pay for a large chunk of the bill with economic stimulus money that has not yet been spent.

Other Republicans are proposing even more drastic changes. Senator Orrin G. Hatch of Utah would block a proposed expansion of Medicaid to all Americans earning less than 133 percent of the federal poverty line, an initiative seen as crucial to reducing the number of uninsured.

Democrats have an array of amendments that would make similarly radical changes, and that could potentially make it difficult for Ms. Snowe, or even some centrist Democrats, to support the bill.

Mr. Rockefeller, for instance, would strike out the proposed creation of private, nonprofit health insurance cooperatives, which are an alternative to the public option. He would alter the proposal to create state-based insurance marketplaces and instead form a single, national insurance exchange. In stark contrast with partisans on both sides, Ms. Snowe’s amendments seek to keep the core proposal intact, while making various adjustments aimed at making sure people can afford the health coverage they would be compelled to buy and also making it easier for people who are offered coverage through their employers to seek alternatives.

In all, Ms. Snowe filed 21 amendments on her own, four more with Democrats, and one other with a Democrat and a Republican  further evidence that she seems closer to Democrats than her own party on the health care proposal.

For those watching the Finance Committee proceedings, which are scheduled to begin Tuesday, keep an eye out for amendments in these key areas:

AFFORDABILITY Mr. Baucus, pressed by Democrats and Ms. Snowe, is expected to increase the government subsidies to help moderate-income individuals and families buy insurance, and make subsidies easier to obtain.

TAXES Several Democrats will push to expand the bill in part by capping tax deductions for high-income Americans at the 35 percent tax bracket, an idea that many Republicans oppose. Republicans, meanwhile, will be pushing to eliminate new taxes on various sectors of the health industry. And there will be all sorts of wrangling over the proposed new tax on the most expensive insurance plans, those costing more than $8,000 for individuals and $21,000 for families.

MEDICARE AND MEDICAID Republicans will fight proposed reductions in government spending on Medicare; Senator Bill Nelson, Democrat of Florida, will push to insulate some participants in plans, called Medicare Advantage, that are sold by private insurers to the elderly. Some Republicans will try to block a proposed expansion of Medicaid, the state-federal insurance program for the poor; while in other cases there will be fights over the potential added costs to states.

Robert Pear contributed reporting.

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Health »A version of this article appeared in print on September 21, 2009, on page A16 of the New York edition.